BRIDGE LENGTH AND SPAN LENGTH: PRESENTING A CORRECT PERSPECTIVE
- GHAI INDERJIT
- Mar 9
- 3 min read
Updated: 4 days ago
Purpose:
To RAISE awareness amongst the practicing engineers about the key differences between the two terms “Bridge Length” and “Span Length”. Understanding this distinction is Crucial, as it has significant financial and functional implications. Therefore, when preparing Contract Agreements, Schedules, Tender Drawings and Construction Drawings, it is essential to accurately differentiate between these two terms.
Description:
In recent times, particularly with the introduction of Engineering Procurement and Construction (EPC), Hybrid Annuity Mode (HAM) project implementation system, it has become evident that there is frequent Confusion regarding the terms "Span" and "Length" of Bridge in project documentation. This misunderstanding is often perpetuated by Design Consultants who misinterpret these terms in Detailed Project Report (DPR) and Design Documents. As a result, there are Contradictory or Incorrect references in the project schedules and tender drawings, which often go Unnoticed by the reviewing and approving Authorities. Furthermore, the Design Engineers employed by Contractors sometimes Exploit this ambiguity in the documentation to their advantage, as demonstrated in following examples:
A. Practical Examples
Some examples as considered in Schedules and Tender Drawings of EPC / HAM Contracts and proposed / constructed by contractors at site are as follows:
1.0 Span 1 x 40 meter
1.1 Mentioned in Schedule B:
Span:1x 40 m and Total Length 1x 40 meter
1.2 Tender GAD
2.0 SPAN 1 X 62 meter
2.1 Mentioned in Schedule B:
Span:1x 62 m and Total Length 1x 62 meter
2.2 Tender GAD
2.3 Proposed by Contractor
3.0 SPAN 1 x 24.4
3.1 Mentioned in Schedule B:
Span:1x 24.4 m and Total Length 1x 24.4 meter
3.2 Tender GAD
3.3 Executed at site by contractor
4.0 SPAN 2 X 25 meter
4.1 Mentioned in Schedule B:
Span:2x 25 m and Total Length 50.0 meter
4.2 Tender GAD
4.3 Executed at site by contractor
B. Span and Length of Bridge as per Specification and Standards
B1. As per IRC:05
B2. As per MORT&H Standard Drawings
B3. As per Railway Standard Drawings
Technical and Finacial Impacts on this account
I. The Clear Space between end supports gets reduced
II. The waterway in case of Bridges is reduced.
III. Financial Implication of Rs 15 Lacs (approximately) per span for a two-lane bridge.
IV. Dispute and Litigations leading to Time and Finance Loss.
Conclusion
From the above examples, it is clear that in the Schedules the values listed for the Span Length and Bridge Length are Identical. However, the Tender GAD's, the Span and Bridge Length differ from those in Schedules. In the Contractor's proposal the Bridge Length is based on the Value in the Schedule, but the Span Length is shorter than the Scheduled value. Ideally, the Bridge Length should be Greater than the Span Length.
Bridge Length > Span Length
There appears to be a lack of attention from stake holders involved in preparing Schedules, Tender GAD, and the Approving/Accepting Authorities. All Engineers should be well aware of the distinct difference between these two terms.
Suggestions
When preparing the Technical Schedules and Tender Drawings, it is Crucial that the Span and Length of the Bridge are clearly defined as outlined in IRC:05. These details should be thoroughly reviewed and validated by the Approving Authorities before finalising the Bid Documents. Practicing Engineers must pay careful attention to this aspect and ensure that their subordinate and Junior Staff are properly trained to include these values in the Documents.
Reference:
a. IRC:05
b. MORT&H Standard Drawings
c. Some of the Drawings and Data available with the author.
Span Length mentioned in Schedule defines the Eligibility of. Bidder / Contractor/ Concessionaire also . Refer the following details from a RFP available on line
Eligible projects shall include following:
(a)Widening / reconstruction / up-gradation works on NH / SH/Expressway ……
If any Major Bridge/ ROB/ Flyover/ Tunnel is (are) part of the project, then the sole Bidder or in case the Bidder being a Consortium, any member of the Consortium shall necessarily demonstrate additional experience in construction of Major Bridge/ ROBs/ Flyovers/ Tunnel in the last 10 (Ten) financial years preceding the Bid Due Date i.e. shall have completed at least one similar Major Bridge/ ROB/ Flyover having span equal to or greater:
In case, longest span of Bridge/ROB/Flyover is less than or equal to 60m, no additional qualification is required.
When longest span is more than 60m: 50% of the longest span or 100m, whichever is less, of the structure proposed in this project.
Agree with your views Ghai Sab. IRC:5 clearly differentiates between bridge length (to be measured between inner faces of dirt walls) and span (to be measured between the center lines of adjacent supports). Span for intermediate piers shall be center to center of piers/supports. For end span, it will be measured from the center of bearing on abutment and to center of adjacent pier. Normally C/C of bearings is called "Effective span", the term not defined in IRC:5. In your views, you may add this too.
1. Bridge span is a technical term used by designer while designing. This term should not be used at all in commercial documents, including schedule B, specifying scope etc. After all, why can’t one reduce the span of superstructure by creating overhanging pier or abutment cap. There is no need to kill creativity of designer.
2. It should be waterway at defined HFL which should determine the requirement of a bridge in case of a water body crossing or in case of flyover clear minimum distance (horizontal and vertical) between obstruction to traffic flow.
Clearly Differentiate both terms.It is very helpful
Good Work.Keep it up.
Bridge Length:
The total length of the bridge structure from one abutment (or approach) to the other.
It includes all spans, expansion joints, and possibly approach slabs.
Measured along the centerline of the bridge from one end to the other.
Span Length:
The distance between two consecutive supports (piers or abutments).
It represents the individual segment of the bridge between two supports.
Can vary within a bridge depending on design requirements.
For example, if a bridge has three spans of 30m, 40m, and 30m, the bridge length is 100m, while the span lengths are 30m, 40m, and 30m, respectively.
You have given a clear understanding of the fundamental knowledge a Bridge Engineer should have while preparing the Schedule for Authority. In fact as an additional check both the span and the length of the structure should be mentioned in the Schedule for bridges as well as grade separated structures.
Understanding these fundamental concepts is crucial. Without this knowledge, serious complications can arise, making post-construction rectifications challenging.
Your explanation is clear and well-articulated. Great effort in educating everyone involved in the growing construction industry!
Keep educating and sharing your knowledge!
In Railways, span is actually the clear span which is to be measured from the face of bed blocks in a waterway opening.
I think span length should be distance between expansion joint to expansion joint or centre of pier to centre of pier in case of continuous beam. Distance between bearing to bearing is effective span not span length.